Patent GB-590914-A (GB)
Title: Process for the manufacture of artificial silk resembling wool
IPC: D02G1/02
Filed: 1945-02-05
Abstract: Yarns consisting wholly or in part of natural or regenerated cellulose filaments or yarns consisting of filaments of a wholly synthetic nature are given a crimped wool-like character by treating them with a strong swelling agent, imparting a temporary high twist thereto with the aid of a false twist device, and arresting the swelling while the yarns are in the highly twisted condition by treatment with water or an aqueous saline solution. Regenerated cellulose filaments or staple fibre yarns made by the viscose or cuprammonium process, or cotton, flax or other bast fibre yarns, or mixed yarns, or yarns of a wholly synthetic nature such as polyamide, polyvinyl chloride or polyurethane yarns which may or may not be used in conjunction with cellulosic yarns, may be treated <PICT:0590914/IV/1> <PICT:0590914/IV/2> according to the invention. Suitable swelling agents which in some cases may be employed at a raised temperature are aqueous solutions of caustic soda, caustic potash, zinc chloride, calcium thiocyanate, sulphuric acid and organic swelling agents diluted with water if desired, such as ethylene chlorhydrin for polyamide yarns and xylene for polyvinyl chloride yarns.  Cellulosic yarns treated according to the invention may be finally treated with formaldehyde at a raised temperature, in the presence of an acid catalyst in order to lower their swelling capacity.  If desired, the treated yarns may be finally cut into staple fibres.  A suitable false twist device for use with the invention comprises a driven sleeve A, Fig. 1, in which is located a roller B around which the yarn is looped.  Referring to Fig. 2, the yarn is led through a bath 4 of swelling agent and is given a false twist between pairs of rollers 2 and 6 by a device 5.  A spraying device 7 serves to remove the swelling liquor from the yarn in the highly twisted condition.  In a modification, two false twist devices rotating at equal speeds in the same direction are employed between the rollers 2 and 6 so as to allow the high twist to persist for some time between the two.  When a temporary high twist is given to a cellulosic staple fibre yarn in a reverse direction to that of the original twist, a continuous filament yarn may be incorporated therewith in order to prevent the yarn from falling apart in passing over the zero point.  Alternatively two staple fibre yarns may be conjointly passed through the false twist device, or an endless runner may be passed through the false twisting apparatus in conjunction with a cellulosic staple fibre yarn.  The endless runner is composed of a material inert to the swelling agent concerned as, for example, a continuous polyvinyl chloride, polyamide, or polyurethane filament yarn or a cellulosic yarn made insensitive to swelling by treatment with formaldehyde, or endless metal strings. Examples are given in which (1) a twisted viscose silk yarn (70 T/mS) is passed through a swelling bath of aqueous caustic potash, squeezed, given a temporary high twist (900 T/mZ) and sprayed with boiling water while in the highly twisted condition.  The yarn in its original twisted condition is then washed, dried and steamed; (2) two spun rayon yarns (400 T/mZ) are impregnated with caustic soda solution at 80 DEG  C., given a temporary high twist (1100 T/mS) and the swelling agent removed by a solution of sulphuric acid containing sodium sulphate.  The yarns in their original twisted condition are reeled separately, washed and dried; (3) two twisted viscose silk yarns are doubled and impregnated with caustic potash solution at 80 DEG  C., squeezed, given a temporary high twist in the same direction as the "doubled" twist, the swelling agent being removed with hot water and in their original doubled condition the yarns are washed, dyed, dried and treated in an aqueous solution containing formaldehyde and aluminium thiocyanate, after which they are dried, heated at 120 DEG  C., and finally steamed. Specifications 424,880, 442,073, 464,981, [all in Group IX], and 572,140 are referred to.